The present invention relates to a device for generating various laser wavelengths from the same laser medium by using resonator mirrors.
In the past, a change between various laser wavelengths from one laser medium (e.g. Ar+, Kr+, Nd:YAG laser) was effected by changing the resonator mirror or by inserting frequency selective elements into the laser resonator (e.g. dye lasers). Frequency selective elements in this sense are, for example, prisms or doubly refracting filters (Lyot filters), Fabry-Perot filters or gas pressure cells. The desired effect is obtained by tilting or turning the components or by changing the gas pressure.
The tuning range realizable with these above-mentioned elements is limited by the spectral widths of the laser emission conditions made possible by the resonator mirror coatings. If the requirements of the user cannot be met by the standard supply of resonator mirrors, an expensive and time consuming development of special resonator mirror coatings becomes necessary. The realizable speed of the switch between various laser wavelengths is limited by the relatively large mechanical adjustment paths that become necessary. If frequency selective intracavity elements are employed, on the other hand, only a very narrow spectral range can be brought to emission at any one time. Light intensity control and regulation is customarily effected by a change in the pumping power or by additional intracavity elements (e.g. iris aperture). Although light intensity regulation is possible with these methods, it requires additional engineering expenses or is possible only within narrow limits and/or at a slow regulating speed (see for example, Spectra-Physics, U.S.A.; Instruction Manual 171 Ion Laser (C/171 9/77)).